In addition to the above-mentioned capabilities of LTE, newer releases from 3GPP have made this technology even more powerful by adding higher order of MIMO, beam-forming, carrier aggregation, and space-time coding (STC).
LTE gets Mission Critical
As defined by 3GPP, mission critical stands for quality or characteristic of a communication activity, application, service or device, that requires low setup and transfer latency, high availability and reliability, ability to handle large numbers of users and devices, strong security and priority and pre-emption handling. This definition very well captures the applicability of LTE for defense.
In release 12 of 3GPP LTE standards, two specific enhancements in LTE were identified to address public safety applications, namely, Proximity Services (ProSe) and Group Communication System Enablers for LTE (GCSE_LTE). Proximity services consists of two main elements: network assisted discovery of users with a desire to communicate with those who are in close physical proximity, and the facilitation of direct communication between such users with, or without, supervision from the network. The definition of proximity services includes some features that are exclusively for public safety applications in public safety spectrum. In the feature “User equipment to network relay” one mobile acts as a relay for another and provides access to network services outside the normal network coverage area. In the feature “User equipment to user equipment relay” one mobile acts as a relay point between two others and allows communication to take place without going via the network even if the communicating mobiles are out of range for direct communication.
Release 14 of 3GPP LTE standards has defined features and enhancements specifically for mission critical applications. Under the heading of mission critical, features like mission critical push to talk (MCPTT), mission critical video over LTE (MCVideo) and mission critical data over LTE (MCData) have been introduced. Under this heading, multiple study topics have been identified such as mission critical security enhancements, mission critical system migration and interconnect between MCPTT systems, mission critical communication interworking with LTE and non-LTE systems, protocol enhancements for MCPTT over LTE and security of the mission critical service.
3GPP has been cognizant of the mission critical requirements which is to develop systems that are highly robust and can address the specific communication needs of emergency services. The study item on mission critical communication interworking with LTE and non-LTE systems emphasizes the use case to make LTE work with public safety standards – such as P25, TETRA and legacy LMR. These public safety standards have so far provided a set of features that were not previously supported in commercial cellular systems.
The MCPTT Service is intended to support communication between several users (a group call), where each user can gain access to the permission to talk in an arbitrated manner. However, the MCPTT Service also supports Private Calls between pairs of users. The MCPTT Service builds on the existing 3GPP transport communication mechanisms provided by the Evolved Packet System (EPS) architectures to establish, maintain, and terminate the actual communication path(s) among the users. The MCPTT Service also builds upon service enablers like GCSE_LTE and ProSe.
MCVideo defines a service for Mission Critical video communication using LTE transport networks. Mission Critical refers to meeting the needs of agencies providing Public Safety services such as, but not limited to, Police, Fire and Ambulance services. Surveillance cameras could also use the MCVideo service in which case, in addition to the existing video storage and monitoring activity already used for the surveillance camera, authority may be given to users in the MCVideo system to connect to, control, receive and forward video either to an individual or to a group. Although the service is designed for transport over commercial and dedicated LTE networks it is not expected to be limited to use over LTE.
MCData service is aimed to provide a means to manage all data connections of mission critical users in the field and provide relevant resources to the ones who need it. For example mission critical users already use event manager software along with the voice system. The migration to LTE networks will allow mission critical users to operate current and new data services whilst relying on the fundamental capabilities of mission critical communication such as defined for MCPTT and Mission Critical Services Common Requirements (MCCoRe). The MCData Service provides a set of communication services that will be directly used by the user or functions that will be called by external applications in control rooms. The MCData Service will reuse functions including end-to-end encryption, key management, authentication of the sender, etc. defined in MCCoRe in order to provide group communications for data services. In addition, the MCData Service will provide a set of generic capabilities such as: messaging, file distribution, data streaming, IP proxy, etc. Also, the MCData Service will provide specific services such as conversation management, data base enquiries, internet access, robots control.